Recently, because the ink-jet recording method can produce an image simply and at low cost, it is applied to various printing fields such as photography, each kind of printing, and special printing such as marking and color filter. Particularly, for the recording apparatus by which a fine dot is jetted and controlled, the ink whose color reproduction area, durability, and jetting property are improved, and an exclusive use sheet in which the adsorptivity of the ink, coloring property of the coloring material, surface glossiness are greatly increased, are used, and the image quality equal to the silver halide photograph can be obtained. The increase of the image quality of today's ink-jet recording system is attained only when all of the exclusive recording apparatus, the exclusive ink, and exclusive recording sheet are present.
However, in the ink-jet system for which the exclusive recording sheet is necessary, the recording medium is limited and the cost up of the recording medium become a problem. Accordingly, many trials to record onto the recording medium different from the exclusive recording sheet by the ink-jet system are made. Specifically, a phase-changing ink-jet system in which a wax ink being solid at a room temperature is used, a solvent type ink-jet system in which the ink in which a quick dry type organic solvent is a main component, is used, or a UV ink-jet system in which, after the recording, a bridge is formed by the ultra violet ray (UV).
In them, the UV ink-jet system is comparatively low odious smell comparing to the solvent type ink-jet system, and for the point which can record onto the recording medium not having the quick dry property and ink adsorptivity, it is being remarked recently, and for example, in Japanese Examined Patent Publication No. H5-54667, Japanese Unexamined Patent Application Publication No. H6-200204, and Japanese Translation of PCT Publication No. 2000-504778, the ultraviolet ray hardenable ink-jet ink is disclosed.
However, even when these inks are used, because a dot diameter after an ink impact is largely changed due to the kind of the recording material or the working environment, it is impossible to form the highly minute image onto all the recording materials.
For example, as this ultraviolet ray hardenable ink, there are a radical polymerization type ultraviolet ray hardenable ink and a cation polymerization type ultraviolet ray hardenable ink, centering around the acrylic component.
The radical polymerization type ultraviolet ray hardenable ink has a problem in which, in its polymerization mechanism, the hardening property is decreased because it is subjected to the oxygen inhibition action under the environment in which the oxygen is present. On the one hand, although the cation polymerization type ultraviolet ray hardenable ink is not subjected to the oxygen inhibition action, in the nature of the polymerization reaction, there is a problem in which it is easily subjected to the influence of water(humidity) of the molecular level.
Further, the ink used for the conventional ultraviolet ray hardenable ink-jet system sometimes has a problem in the safety such as skin irritation, causing sensitivity, or abnormal chromosome, and particularly, in the soft package printing or label printing including the food package, the actual situation is that the active ray hardenable ink-jet system is difficult to come to practical use.